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  <!-- Copyright 2018 Paul Fultz II
     Distributed under the Boost Software License, Version 1.0.
     (http://www.boost.org/LICENSE_1_0.txt)
--><div class="section" id="configurations">
<h1>Configurations<a class="headerlink" href="#configurations" title="Permalink to this headline">¶</a></h1>
<p>There are several configuration macros that control the behavior of Boost.HigherOrderFunctions library.</p>
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<tr class="row-odd"><th class="head">Name</th>
<th class="head">Description</th>
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<tr class="row-even"><td><code class="docutils literal"><span class="pre">BOOST_HOF_CHECK_UNPACK_SEQUENCE</span></code></td>
<td>Unpack has extra checks to ensure that the function will be invoked with the
sequence. This extra check can help improve error reporting but it can slow
down compilation. This is enabled by default.</td>
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<tr class="row-odd"><td><code class="docutils literal"><span class="pre">BOOST_HOF_NO_EXPRESSION_SFINAE</span></code></td>
<td>This controls whether the library will use expression SFINAE to detect the
callability of functions. On MSVC, this is enabled by default, since it does
not have full support for expression SFINAE.</td>
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<tr class="row-even"><td><code class="docutils literal"><span class="pre">BOOST_HOF_RECURSIVE_CONSTEXPR_DEPTH</span></code></td>
<td>Because C++ instantiates <cite>constexpr</cite> functions eagerly, recursion with
<cite>constexpr</cite> functions can cause the compiler to reach its internal limits. The
setting is used by the library to set a limit on recursion depth to avoid
infinite template instantiations. The default is 16, but increasing the limit
can increase compile times.</td>
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